                    [:m :ft]                   #(* % (factors [:m :ft]))
                    [:kg :lb]                  #(* % (factors [:kg :lb]))
                    [:lb :kg]                  #(/ % (factors [:kg :lb]))
-                   [:lb-per-gal :kg-per-m3]   #(* % (factors [:lb-per-gal :kg-per-m3]))
-                   [:kg-per-m3 :lb-per-gal]   #(/ % (factors [:lb-per-gal :kg-per-m3]))
                    [:m3-per-min :bpm]         #(* % (factors [:m3 :bbl]))
                    [:bpm :m3-per-min]         #(/ % (factors [:bbl :m3]))
                    [:F :C]                    #(/ (- % 32) 1.8)

                            :length                 [:ft :m]
                            :mass                   [:lb :kg]
                            :power                  [:hp :W]
                            :proppant-concentration [:lb-per-gal :kg-per-m3]
                            :slurry-rate            [:bpm :m3-per-min]
                            :volume                 [:bbl :m3]
                            :temperature            [:F :C]}]

                   [:ft-lb :J]                1.35582
                   [:m :ft]                   3.28084
                   [:kg :lb]                  2.20462262185
                   ;; slurry rate conversion not needed (use [:bbl :m3])
                   [:m3 :bbl]                 6.28981077}
        converter {[:lb-per-cu-ft :kg-per-m3] #(* % (factors [:lb-per-cu-ft :kg-per-m3]))
